Hyperpolarization of water from UV radicals to study water dynamics in proteins

• Applicant: Dr. Fabian Hecker
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 530727077

This research proposal aims at developing and establishing an experimental methodology to study water dynamics in and around proteins using hyperpolarized water (HyperW) generated by dissolution dynamic nuclear polarization (dDNP) with non-persistent radicals. Water molecules can influence the structure and function of biological macromolecules - therefore, experimental methods to study them are of high interest. Nuclear magnetic resonance spectroscopy, which detects the difference in populations of nuclear spin states, i.e., spin polarization, is among the most applied techniques to study biomolecules in their physiological surrounding. Hyperpolarization techniques such as dissolution DNP increase the inherently low NMR signals by transferring high electron spin polarization to the nuclear spins. Hyperpolarized water from dDNP has been established as a universal sensitivity booster for NMR experiments, as HyperW protons can be transferred to biomolecules via chemical exchange. dDNP is an ex-situ method that requires transporting the hyperpolarized sample from a polarization magnet to a detection system. Transport is the most critical step since the organic radicals necessary for hyperpolarization are also the primary source of signal loss (relaxation). A new experimental strategy utilizes non-persistent organic radicals generated through high-power UV irradiation that are only stable below 200 K. These radicals can be eliminated before the transport, resulting in larger and longer-lasting polarizations. Here we plan to establish experimental protocols for multidimensional NMR experiments with UV-HyperW. The benefit of longer relaxation and higher overall polarization will be harnessed. New NMR protocols will be developed to investigate water exchange and residence time dynamics on the surface of and inside the biomolecules. Both project steps will utilize a suitable model system, which is a small protein that houses tightly bound water molecules that influence subtle protein structure dynamics. In the second part, we will develop the experimental protocol to investigate large biomolecules with UV-HyperW. First, the hyperpolarization of water with polarizing agents for long-lasting proton solid-state polarization will be developed to transport HyperW samples to a high-field NMR facility. For this, the properties of non-persistent radicals will be investigated with high-resolution electron paramagnetic resonance spectroscopy and standard DNP NMR experiments. Finally, we will utilize UV-HyperW, transported to a high-field NMR facility, to investigate large biomolecules above the typical resolution limit of multidimensional NMR.

• DFG Programme: WBP Fellowship
• International Connection: Denmark
• Host: Dr. Mathilde Hauge Lerche